1. Field of the Invention
The present invention relates to multilayer ceramic electronic components, for example, multilayer ceramic capacitors and multilayer ceramic thermistors, and in particular, to a multilayer ceramic electronic component including a floating internal electrode disposed in a ceramic element assembly and including a plurality of effective regions used to extract capacitance.
2. Description of the Related Art
Automobiles include various incorporated systems, including an engine, an air conditioner, and an air bag system. A plurality of control devices for controlling each of these systems, called electrical control units (ECUs), are incorporated, accordingly. Each ECU has various mounted electronic components. In recent years, with an increase in the number of systems, the number of ECUs incorporated in an automobile has increased. As such, miniaturization of an ECU and an electronic component mounted on the ECU is highly demanded. Thus, multilayer ceramic electronic components, such as multilayer ceramic capacitors, are widely used.
For a multilayer ceramic electronic component, externally applied stress, such as thermal stress due to a change in external temperature or flexural stress imposed on a mounting board, may cause a crack to occur in a ceramic element assembly. If the crack runs over the border between internal electrodes coupled to different potentials, a short-circuit may occur.
A structure to prevent such a short circuit is disclosed in Japanese Unexamined Patent Application Publication No. 6-163311 listed below. FIG. 10 is a front cross-sectional view that illustrates a multilayer ceramic capacitor described in Japanese Unexamined Patent Application Publication No. 6-163311. For a multilayer ceramic capacitor 101, a plurality of first internal electrodes 103 and a plurality of second internal electrodes 104 are arranged within a ceramic element assembly 102. The plurality of first internal electrodes 103 are extended to a first end surface 102a of the ceramic element assembly 102, and the plurality of second internal electrodes 104 are extended to a second end surface 102b of the ceramic element assembly 102. A first external terminal electrode 105 covering the first end surface 102a is arranged so as to be electrically coupled to the plurality of first internal electrodes 103. The first external terminal electrode 105 includes a terminal electrode main section 105a covering the end surface 102a and an extended section 105b continuous with the terminal electrode main section and extending to at least a first principal surface 102c and a second principal surface 102d of the ceramic element assembly 102. Similarly, a second external terminal electrode 106 is provided at the end surface 102b. The external terminal electrode 106 also includes a terminal electrode main section 106a and an extended section 106b. 
The above-described crack caused by thermal stress or flexural stress typically occurs from edges of the extended sections 105b and 106b of the external terminal electrodes 105 and 106 toward the inside of the ceramic element assembly 102. For the multilayer ceramic capacitor 101, the length of a portion in which the first internal electrodes 103 and the second internal electrodes 104 overlap each other with ceramic layers disposed therebetween, that is, the opposing distance Z is smaller than the distance R between the extended sections 105b and 106b. As indicated by the arrow A illustrated in FIG. 10, even if a crack runs from an edge of the extended section 106b toward the inside of the ceramic element assembly 102, the crack is merely located over the second internal electrodes 104 coupled to one potential, so that no short-circuit occurs.
However, an actual crack does not always run from an edge of the extended section 106b in the direction of layering, as indicated by the arrow A. For example, as indicated by the arrow B, a crack may run obliquely from the edge of the extended section 106b and extend to an effective region in which the first and second internal electrodes 103 and 104 are opposed to each other. In that case, a short-circuit disadvantageously occurs.
Japanese Unexamined Utility Model Registration Application Publication No. 54-5755 discloses a multilayer ceramic capacitor including a floating internal electrode and having first and second effective regions arranged within a ceramic element assembly. FIG. 11 is a front cross-sectional view that illustrates the multilayer ceramic capacitor described in Japanese Unexamined Utility Model Registration Application Publication No. 54-5755.
For a multilayer ceramic capacitor 111, a plurality of first internal electrodes 113 extending to a first end surface 112a of a ceramic element assembly 112 are provided within the ceramic element assembly 112. A plurality of second internal electrodes 114 are provided at the same height positions as the plurality of first internal electrodes 113 so as to be extended to a second end surface 112b. First and second terminal electrodes 115 and 116 are formed at the end surfaces 112a and 112b, respectively. The terminal electrodes 115 and 116 include terminal electrode main sections 115a and 116a, respectively, and extended sections 115b and 116b, respectively.
A plurality of floating internal electrodes 117 is arranged within the ceramic element assembly 112. The floating internal electrodes 117 are opposed to the first internal electrodes 113 and the second internal electrodes 114 with ceramic layers disposed therebetween.
Accordingly, in a portion where the plurality of first internal electrodes 113 and the plurality of floating internal electrodes 117 overlap each other with ceramic layers disposed therebetween, a first effective region for extracting capacitance is provided. Similarly, in a portion where the plurality of floating internal electrodes 117 and the plurality of second internal electrodes 114 overlap each other with ceramic layers disposed therebetween, a second effective region for extracting capacitance is provided.
For the multilayer ceramic capacitor 111 described in Japanese Unexamined Utility Model Registration Application Publication No. 54-5755, a first effective region 118 and a second effective region 119 are provided. Accordingly, as indicated by the arrow C1 illustrated in FIG. 11, even if a crack occurs and runs obliquely from an edge of the extended section 115b of the first external terminal electrode 115, a short-circuit is prevented in the second effective region 119.
At the opposite second external terminal electrode 116 side, even if a crack C2 occurs and runs obliquely from an edge of the extended section 116b, as indicated by the arrow C2, and reaches the second effective region, a short-circuit is prevented in the first effective region 118.
Accordingly, in the case of the multilayer ceramic capacitor 101 illustrated in FIG. 10, a short-circuit occurs if an obliquely running crack B occurs. In contrast, for the multilayer ceramic capacitor 111, even if the obliquely running crack C1 or C2 occurs, no short circuit occurs.
However, the cracks C1 and C2 may appear at the same time. In that case, a short circuit disadvantageously occurs.